User interface customization based on speaker characteristics

ABSTRACT

The characteristics of the speaker may be used to automatically customize a user interface of a client device for the speaker. For instance, a mobile device may generate a user interface that does not permit access to particular applications on the mobile device, that only includes options to call home and access a camera application, or that includes an override option to cause generation of a user interface for a different class of user than a user class for the automatic customizations applied to the user interface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/096,608 filed on Dec. 4, 2013, the entirecontents of which is incorporated by reference.

FIELD

This specification describes technologies relates to adjustment of auser interface based on characteristics of a speaker.

BACKGROUND

Client devices may be shared by multiple users, each of which may havedifferent characteristics and preferences.

SUMMARY

Characteristics of a speaker may be estimated using speech processingand machine learning. The characteristics of the speaker, such as age,gender, emotion, and/or dialect, may be used to automatically customizea user interface of a client device for the speaker. The speaker'scharacteristics may also be provided to other applications executing onthe client device to enhance their content and provide a richer userexperience.

In general, one aspect of the subject matter includes the action ofselecting a user profile associated with a user interface. The actionsfurther include, after selecting the user profile, obtaining an audiosignal encoding an utterance of a speaker. The actions also includeprocessing the audio signal to identify at least one characteristic ofthe speaker. And the actions include customizing the user interfaceassociated with the user profile based on the at least onecharacteristic. The characteristic may include, for example, an age,gender, dialect, or emotion of the speaker. Some implementations includethe further action of providing the at least one characteristic of thespeaker to a third-party application.

In some implementations, customizing the user interface associated withthe user profile based on the at least one characteristic may includechanging a font size of the user interface based on the at least onecharacteristic, changing a color scheme of the user interface based onthe at least one characteristic, restricting access to one or moreapplications on the user interface based on the at least onecharacteristic, providing access to one or more applications on the userinterface based on the at least one characteristic, restricting accessto one or more applications provided by the user interface based on theat least one characteristic.

In some implementations, selecting a user profile includes selecting, ata client device, a user profile based on one or more of a password,voice recognition, speech recognition, fingerprint recognition, orfacial recognition. Alternatively or in addition, in someimplementations, selecting a user profile includes selecting, at aclient device, a default user profile for the client device.

In some implementations, processing the audio signal to identify atleast one characteristic of the speaker includes the actions ofproviding the audio signal as an input to a neural network and receivinga set of likelihoods associated with the at least one characteristic asan output of the neural network.

Another general aspect of the subject matter includes the action ofobtaining an audio signal encoding an utterance of a speaker. Theactions further include performing speech recognition, voicerecognition, or both on the audio signal to select a user profileassociated with a user interface. The actions also include processingthe audio signal to identify at least one characteristic of the speaker.And the actions include customizing the user interface associated withthe user profile based on the at least one characteristic. Thecharacteristic may include, for example, an age, gender, dialect, oremotion of the speaker. Some implementations include the further actionof providing the at least one characteristic of the speaker to athird-party application.

In some implementations, customizing the user interface associated withthe user profile based on the at least one characteristic may includechanging a font size of the user interface based on the at least onecharacteristic, changing a color scheme of the user interface based onthe at least one characteristic, restricting access to one or moreapplications on the user interface based on the at least onecharacteristic, providing access to one or more applications on the userinterface based on the at least one characteristic, restricting accessto one or more applications provided by the user interface based on theat least one characteristic.

In some implementations, processing the audio signal to identify atleast one characteristic of the speaker includes the actions ofproviding the audio signal as an input to a neural network and receivinga set of likelihoods associated with the at least one characteristic asan output of the neural network.

Some implementations may advantageously customize a user interface basedon characteristics of a speaker, thus providing a rich user experience.Some implementations also may advantageously provide characteristics ofa speaker to other applications to enhance their content and provide aricher user experience.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other potential features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram that illustrates a client device configured toidentify characteristics of a speaker and customize a user interfacebased on the identified characteristics.

FIG. 2 is a diagram that illustrates an example of processing for speechrecognition using neural networks.

FIG. 3 is a diagram that illustrates an example of processing togenerate latent variables of factor analysis.

FIG. 4 is a flow diagram that illustrates an example of a process forcustomizing a user interface based on characteristics of a speaker.

FIG. 5 is a flow diagram that illustrates another example of a processfor customizing a user interface based on characteristics of a speaker.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Typical client devices do not automatically perform customization basedon characteristics of the person using the device. When users sharedevices, this may mean that the user interface for any given user maynot match that user's preferences. In addition, even when only a singleuser operates a given client device, it may be desirable toautomatically tailor the user interface to settings that may betypically preferred by individuals with the user's characteristics. Forexample, a young child operating a client device may prefer large icons,little or no text, and the ability to play some games and call home. Thechild's parents also may prefer that the client device restrict accessto most applications while the child is using the client device. Asanother example, an elderly individual may prefer large icons and textand unrestricted access to applications on the client device. Bydetecting characteristics of the user, the client device may be able toautomatically customize the user interface to provide such settingswithout requiring the user to manually apply the settings.

As described in this disclosure, a client device may customize a userinterface based on characteristics that it estimates using the speaker'svoice. For example, when a user logs into a client device using a voiceunlock feature with speaker verification and/or uses voice search orvoice input, a speech recording may be made and analyzed by a classifierto identify characteristics of the user. These characteristics mayinclude, for example, the user's age, gender, emotion, and/or dialect.

Once a speech recording is made, a trait classification pipeline may beactivated. The pipeline may include processes at the client deviceand/or a speech recognition server. In the pipeline, a speechrecognition processor could be applied to compute mel-frequency cepstralcoefficients (MFCCs), perceptive linear predictive (PLP), and/orfilterbank energy features. The output of the feature computation stepcould then be provided to a statistical classifier such as a Gaussianmixture model or a neural network trained to classify the features ofinterest. Training data for the classifier could include, for example,voice search logs annotated as corresponding to: child, adult, orelderly speech; male or female speech; happiness or sadness; orregionally dialected speech. Classifications for certain characteristicsmay be determined using other techniques, such as, for example, usingthe pitch characteristics of the speech recording to detect childspeech, or by clustering data for male and female speakers.

Various customizations based on the identified characteristics may beimplemented. Such customizations may be particularly advantageous in thecase of children, who are likely to benefit from a specially customizeduser interface, and who also may be prone to altering preferred settingsof adult users of a device, e.g., by changing settings, deleting files,etc. Additionally, children may be vulnerable to being harmed byunfiltered speech from the Internet, and they may therefore benefit fromhaving the client device automatically provide a “safe mode” thatrestricts web browsing and only allows the use of selected child-safeapplications when child speech is detected. For example, if likely childspeech is detected, the user interface may change to a simplified safemode that allows restricted web browsing and application use. In someimplementations, when child speech is detected, the client device maynot store the child's inputs in search logs or adapt the speaker profileon the client device based on the child's inputs. Some implementationsmay provide an override feature for adult users in case the clientdevice erroneously determines that the user has vocal characteristicscorresponding to child speech. As another example, if elderly speech isdetected, the user interface may provide large icons and text.

The client device may also provide identified characteristics of aspeaker to native or third party applications, for example, in the formof an application programming interface (API). A user may have theoption to selectively enable and/or disable the sharing of theircharacteristics with these other applications. In some implementations,the client device may request access before such an API may beinstalled, in which case the user may affirmatively approve installationof the API.

As described herein, customizing the user interface based oncharacteristics of a speaker should be distinguished from selecting oraccessing a user profile based on voice and/or speech recognition. Someclient devices may allow a user to establish a user profile and store aset of preferences for operating the client device in the user profile.The user profile can include, for example, the files and folders savedby the user; the applications, software, and programs, downloaded to thecomputing device by the user; security settings for loading the userprofile; operation restrictions for the user; user interface of theclient device including font size, icon size, type of wallpaper, iconsto be displayed; and any other items or settings for operation of theuser profile on the client device.

However, customizing the user interface based on the characteristics ofa speaker may be performed in addition to, or instead of, selecting auser profile. For example, in some implementations, the client devicemay perform speech and/or voice recognition to access a user profile andunlock a client device. The same utterance used to access the userprofile may also be analyzed to identify characteristics of the speakerand customize the user interface associated with the user profile.Alternatively or in addition, the client device may access a defaultuser profile and the user may unlock a device using, for example, a PIN,password, username and password, or biometrics. After the client devicehas been unlocked, the user may make an utterance and the client devicemay customize the user interface based on characteristics of the user'svoice.

FIG. 1 illustrates a client device 100 configured to identifycharacteristics of a speaker and customize a user interface 110 based onthe identified characteristics. In particular, a user 102 speaks anutterance 104 into the client device 100, which generates an audiosignal encoding the utterance. The client device 100 then processes theaudio signal to identify characteristics of the user 102. For example,the client device may provide the audio signal to a trained classifier(e.g., a neural network) at the client device 100. Alternatively or inaddition, the client device 100 may provide the audio signal to a server120 via a network 130, and the server then provides the audio signal toa trained classifier at the server. The client device 100 and/or theserver then uses output from the trained classifier to identify voicecharacteristics of the user 102. These voice characteristics are thenused to customize the user interface 110 of the client device. As shownin FIG. 1, the user interface 110 a represents the display of the clientdevice before analyzing the voice characteristics of the user 102, andthe user interface 110 b represents the display after analyzing thevoice characteristics of the user 102.

The client device 100 can be, for example, a desktop computer, laptopcomputer, a tablet computer, a wearable computer, a cellular phone, asmart phone, a music player, an e-book reader, a navigation system, orany other appropriate computing device. The functions performed by theserver 120 can be performed by individual computer systems or can bedistributed across multiple computer systems. The network 130 can bewired or wireless or a combination of both and can include the Internet.

In more detail, a user 102 of the client device 100 initiates a speechrecognition session such that the client device encodes an audio signalthat includes the utterance 104 of the user. The user may, for example,press a button on the client device 100 to perform a voice search orinput a voice command or hotword, speak an utterance, and then releasethe button on the client device 100. In another example, the user mayselect a user interface control on the client device 100 before speakingthe utterance. As another example, the user 102 may activate a voiceunlock feature on the client device 100 by speaking an utterance. Theclient device 100 encodes the utterance into an audio signal, which maybe, for example, a snippet of relatively high quality audio, such as 16kHz lossless audio.

In some implementations involving a voice unlock feature, the clientdevice 100 may perform speech and/or voice recognition on the utteranceto identify the speaker as an authorized user of the device and thenunlock the device. For example, the client device 100 and/or the server120 may compare a voice signature of the utterance with one or morevoice signatures associated with authorized users that are stored on theclient device. Alternatively or in addition, the client device 100and/or the server 120 may perform speech recognition on the utterance toidentify an authorized password or phrase associated with an authorizeduser of the client device. In some aspects, different users of the sameclient device 100 may each establish a user profile that includespreferences for operating the client device associated with the user andthe applications of interest to the user. Each user profile may also beassociated with one or more voice signatures, passwords, and/orpassphrases. When the client device 100 identifies a voice signature,password, and/or passphrase associated with a user profile, the clientdevice select the associated user profile, unlock the client device, andprovide access to that user profile.

The client device 100 and/or the server 120 then identify audiocharacteristics. These audio characteristics may be independent of thewords spoken by the user 102. For example, the audio characteristics mayindicate audio features that likely correspond to one or more of thespeaker's gender, the speaker's age, speaker's emotional state, and/orthe speaker's dialect. While feature vectors may be indicative of audiocharacteristics of specific portions of the particular words spoken, theaudio characteristics may be indicative of time-independentcharacteristics of the audio signal.

As discussed further below, the audio characteristics can include latentvariables of multivariate factor analysis (MFA) of the audio signal. Thelatent variables may be accessed from data storage, received fromanother system, or calculated by the client device 100 and/or the server120. To obtain the audio characteristics, feature vectors derived fromthe audio signal may be analyzed by a factor analysis model. The factoranalysis model may create a probabilistic partition of an acoustic spaceusing a Gaussian Mixture Model, and then average the feature vectorsassociated with each partition. The averaging can be a soft averagingweighted by the probability that each feature vector belongs to thepartition. The result of processing with the factor analysis model canbe an i-vector, as discussed further below.

In the illustrated example, the client device 100 and/or the server 120inputs the audio characteristics into a trained classifier 125. Theaudio characteristics may be represented by, for example, an i-vectorand/or acoustic features such as MFCCs or PLPs. The classifier may be,for example, a Gaussian mixture mode, a neural network, a logisticregression classifier, or a support vector machine (SVM). The classifierhas been trained to classify the features of interest. Training data forthe classifier could include, for example, voice search logs annotatedas corresponding to: child, adult, or elderly speech; male or femalespeech; or regionally dialected speech. Classifications for certaincharacteristics may be determined using other techniques, such as, forexample, using the pitch characteristics of the speech recording todetect child speech, or by clustering data for male and female speakers.As another example, in some implementations, the dialect may bedetermined by the client device 100 and/or the server 120 using theautomated dialect-identifying processes described, for example, in D.Martinez, O. Plchot, L. Burget, Ondrej Glembek, and Pavel Matejka,“Language Recognition in iVectors Space.,” INTERSPEECH., pp. 861-864,ISCA (2011); K. Hirose et al., “Accent Type Recognition And SyntacticBoundary Detection Of Japanese Using Statistical Modeling Of MoraicTransitions Of Fundamental Frequency Contours,” Proc. IEEE ICASSP'98(1998); T. Chen et al., “Automatic Accent Identification using GaussianMixture Models,” IEEE Workshop on ASRU (2001); or R. A. Cole, J. W. T.Inouye, Y. K. Muthusamy, and M. Gopalakrishnan, “Language identificationwith neural networks: a feasibility study,” Communications, Computersand Signal Processing, 1989 Conference Proceeding., IEEE Pacific RimConference on, 1989, pp. 525-529. As another example, emotions of aspeaker may be classified using techniques such as those described in K.Rao, S. Koolagudi, and R. Vempada, “Emotion Recognition From SpeechUsing Global and Local Prosodic Features,” Int'l Journal of SpeechTechnology, Vol. 16, Issue 2, pp. 143-160 (June 2013) or D. Ververidis,C. Kotropoulos, “Emotional speech recognition: Resources, features, andmethods,” Speech Communication 48, pp. 1162-81 (2006).

The classifier then outputs data 127 classifying various characteristicsof the speaker. For example, the classifier may output a set oflikelihoods for the speaker's age, gender, emotion, and/or dialect. Inparticular, the output may be a normalized probability between zero andone for one or more of these characteristics. Output for a genderclassification may be, for example, male—0.80, female—0.20. Output foran age classification may be, for example, child—0.6, adult—0.3,elderly—0.1. Output for an emotion classification may be, for example,happy—0.6, angry—0.3, sad—0.1. Output for a dialect classification maybe, for example, British English—0.5, Kiwi English—0.2, IndianEnglish—0.1, Australian English—0.1, Irish English—0.1.

The client device 100 and/or the server 120 then identifiescharacteristics of the user 102 based on the output of the classifier.For example, the client device and/or the server 120 may select thecharacteristics having the highest probability. To continue the exampleabove, the client device and/or the server 120 may identify the user 102as a male child speaking British English. In some cases, the clientdevice 102 may apply a minimum threshold probability to the selection.In such instances, where the classifier does not identify acharacteristic as having a probability that exceeds the threshold, theclient device 100 and/or server 120 may select a default characteristicsuch as “unknown,” may prompt the user for additional information,and/or may cause an error message to be outputted to the user 102 (e.g.,“please say that again,” or “please provide additional information”).

Once the characteristics of the user 102 have been identified, theclient device 100 customizes the user interface 110 based on thesecharacteristics. Customizing the user interface 110 may include, forexample, changing layout, font size, icon size, color scheme, wallpaper,icons and/or text to be displayed, animations, and any other items orsettings for operation of the client device. Customizing user interfacemay also include, for example, restricting and/or modifying theoperation of one or more applications executing on the client device.The specific customizations that will correspond to variouscharacteristics may be determined based on user information, demographicinformation, surveys, empirical observations, and/or any other suitabletechniques.

For example, to continue the example where the user 102 has beenidentified as a male child speaking British English, the client devicemodifies the user interface to correspond to a child safe mode. Inparticular, before analyzing the voice characteristics of the user 102,the user interface 110 a includes a full complement of applications thatmay be accessed, including a camera application, a contact application,a calendar application, a search application, a messaging application, abrowser application, a call application, and an email application. Incontrast, after analyzing the voice characteristics, the user interface110 b has been modified to permit access only to a camera applicationand a phone call application. The icons for both of these applicationshave also been enlarged to make it easier for children to understand andoperate. In some implementations, the user interface 110 b for a childmode may also restrict or modify the operations of the applications thatare accessible, for example by limiting the phone numbers that can becalled (e.g., only able to call home), limiting the number of picturesthat can be taken, or restricting the websites that can be accessed. Forexample, the client device 100 may provide information regarding thecharacteristics of the user to native and/or third-party applicationswith an API on the client device, which the applications may use tomodify their operations.

For situations in which the systems discussed here collect personalinformation about users, or may make use of personal information, theusers may be provided with an opportunity to control whether programs orfeatures collect personal information (e.g., information about a user'ssocial network, social actions or activities, profession, a user'spreferences, or a user's current location), or to control whether and/orhow to receive content from the content server that may be more relevantto the user. In addition, certain data may be anonymized in one or moreways before it is stored or used, so that personally identifiableinformation is removed. For example, a user's identity may be anonymizedso that no personally identifiable information can be determined for theuser, or a user's geographic location may be generalized where locationinformation is obtained (such as to a city, ZIP code, or state level),so that a particular location of a user cannot be determined. Thus, theuser may have control over how information is collected about him or herand used by a content server.

FIG. 2 is a diagram 200 that illustrates an example of processing forspeech recognition using neural networks. The operations discussed aredescribed as being performed by the server 120, but may be performed byother systems, including combinations of the client device 100 and/ormultiple computing systems. While the example architecture describedwith reference to FIG. 2 includes i-vector inputs into a neural networkclassifier, the present disclosure is not limited to this architecture.For example, any suitable inputs representing audio characteristics ofthe speaker, such as MFCCs, or PLPs, could be used. In particular, aneural network could be trained directly from acoustic features (MFCCsor PLPs), e.g., a neural network could receive an MFCC vector (X) andpredict the characteristic that maximizes P(L|X) in a similar manner asdescribed below. As another example, any suitable classifier may be usedsuch as an SVM or logistic regression.

The server 120 receives data about an audio signal 210 that includesspeech to be recognized. The server 120 or another system then performsfeature extraction on the audio signal 210. For example, the server 120analyzes different segments or analysis windows 220 of the audio signal210. The windows 220 are labeled w₀ . . . w_(n), and as illustrated, thewindows 220 can overlap. For example, each window 220 may include 25 msof the audio signal 210, and a new window 220 may begin every 10 ms. Forexample, the window 220 labeled w₀ may represent the portion of audiosignal 210 from a start time of 0 ms to an end time of 25 ms, and thenext window 220, labeled w₁, may represent the portion of audio signal120 from a start time of 10 ms to an end time of 35 ms. In this manner,each window 220 includes 15 ms of the audio signal 210 that is includedin the previous window 220.

The server 120 performs a Fast Fourier Transform (FFT) on the audio ineach window 220. The results of the FFT are shown as time-frequencyrepresentations 230 of the audio in each window 220. From the FFT datafor a window 220, the server 120 extracts features that are representedas an acoustic feature vector 240 for the window 220. The acousticfeatures may be determined by binning according to filterbank energycoefficients, using an MFCC transform, using a PLP transform, or usingother techniques. In some implementations, the logarithm of the energyin each of various bands of the FFT may be used to determine acousticfeatures.

The acoustic feature vectors 240, labeled v₁ . . . v_(n), include valuescorresponding to each of multiple dimensions. As an example, eachacoustic feature vector 240 may include a value for a PLP feature, avalue for a first order temporal difference, and a value for a secondorder temporal difference, for each of 13 dimensions, for a total of 39dimensions per acoustic feature vector 240. Each acoustic feature vector240 represents characteristics of the portion of the audio signal 210within its corresponding window 220.

The server 120 may also obtain an i-vector 250. For example, the server120 may process the audio signal 210 with an acoustic model 260 toobtain the i-vector 250. In the example, the i-vector 250 indicateslatent variables of multivariate factor analysis. The i-vector 250 maybe normalized, for example, to have a zero mean unit variance. Inaddition, or as an alternative, the i-vector 250 may be projected, forexample, using principal component analysis (PCA) or linear discriminantanalysis (LDA). Techniques for obtaining an i-vector are describedfurther below with respect to FIG. 3.

The server 120 uses a neural network 270 that can serve as an acousticmodel and indicate likelihoods that acoustic feature vectors 240represent different phonetic units. The neural network 270 includes aninput layer 271, a number of hidden layers 272 a-272 c, and an outputlayer 273. The neural network 270 receives an i-vector as input. Forexample, the first hidden layer 272 a has connections from the i-vectorinput portion of the input layer 271, where such connections are notpresent in typical neural networks used for speech recognition.

The neural network 270 has been trained to estimate likelihoods that ani-vector represents various speaker characteristics. For example, duringtraining, input to the neural network 270 may be i-vectors correspondingto the utterances from which the acoustic feature vectors were derived.The various training data sets can include i-vectors derived fromutterances from multiple speakers.

To classify speaker characteristics from the audio signal 210 using theneural network 270, the server 120 inputs the i-vector 250 at the inputlayer 271 of the neural network 270. At the output layer 273, the neuralnetwork 270 indicates likelihoods that the speech corresponds tospecific speaker characteristics. The output layer 273 providespredictions or probabilities for these characteristics given the data atthe input layer 271. The output layer 273 can provide a value, for eachof the speaker characteristics of interest. Because the i-vector 250indicates constant or overall properties of the audio signal 210 as awhole, the information in the i-vector 250 is independent of theparticular acoustic states that may occur at specific windows 220.

In some implementations, the i-vector 250 is based on a currentutterance i-vector derived from the current utterance (e.g., theparticular audio signal 210) being recognized. In some implementations,the i-vector 250 may be a speaker i-vector generated using multipleutterances of the speaker (e.g., utterances from multiple differentrecording sessions, such as recordings on different days). For example,multiple utterances for a speaker may be stored in association with auser profile, and the utterances may be retrieved to update a speakeri-vector for that user profile. To generate a speaker i-vector, ani-vector can be determined for each utterance in the set of multipleutterances of the speaker. The i-vectors can be averaged together togenerate the speaker i-vector. In some implementations, where a speakeri-vector is used rather than an utterance i-vector derived from theutterance being recognized, post processing may discriminative training,such as LDA, to identify attributes that are indicative of speakercharacteristics. For example, various techniques can be used to isolatespeaker characteristics, independent of noise, room characteristics, andother non-speaker-dependent characteristics.

In some implementations, the server 120 may identify the speaker andselect an i-vector based on the speaker's identity. An i-vector may becalculated for each of multiple users, and the i-vectors may be storedin association with user profiles for those users for later use inrecognizing speech of the corresponding users. The server 120 mayreceive a device identifier for a device, such as a mobile phone, thatthe speaker is using to record speech. In addition, or as analternative, the server 120 may receive a user identifier thatidentifies the user, such as a name or user account login. The server120 may identify the speaker as a user that owns the device or a user islogged into a user account on the device. In some implementations, theserver 120 may identify the speaker before recognition begins, or beforeaudio is received during the current session. The server 120 may thenlook up the i-vector that corresponds to the identified user and usethat i-vector to recognize received speech.

In some implementations, a successive approximation technique may beused to approximate and re-estimate the i-vector 250 while audio isreceived. The i-vector 250 may be re-estimated at a predeterminedinterval, for example, each time a threshold amount of new audio hasbeen received. For example, a first i-vector may be estimated using theinitial three seconds of audio received. Then, after another threeseconds of audio has been received, a second i-vector may be estimatedusing the six seconds of audio received so far. After another threeseconds, a third i-vector may be estimated using all nine seconds ofaudio received, and so on. The re-estimation period may occur at longerintervals, such as 10 seconds or 30 seconds, to reduce the amount ofcomputation required. In some implementations, i-vectors arere-estimated at pauses in speech (e.g., as detected by a speech energyor voice activity detection algorithm), rather than at predeterminedintervals.

An i-vector derived from a small segment of an utterance may introducesome inaccuracy compared to an i-vector for the entire utterance, but asmore audio is received, the estimated i-vectors approach the accuracy ofan i-vector derived from the whole utterance. In addition, audio fromrecent utterances (e.g., audio from a predetermined number of mostrecent utterances or audio acquired within a threshold period of thecurrent time) may be used with received audio to estimate the i-vectors,which may further reduce any inaccuracy present in the estimates.

In some implementations, the server 120 transitions from using a firsti-vector to a second i-vector during recognition of an utterance. Forexample, the server 120 may begin by using a first i-vector derived froma previous utterance. After a threshold amount of audio has beenreceived (e.g., 3, 5, 10, or 30 seconds), the server 120 generates asecond i-vector based on the audio received in the current session anduses the second i-vector to process subsequently received audio.

FIG. 3 is a diagram 300 that illustrates an example of processing togenerate latent variables of factor analysis. The example of FIG. 3shows techniques for determining an i-vector, which includes theselatent variables of factor analysis. I-vectors are time-independentcomponents that represent overall characteristics of an audio signalrather than characteristics at a specific segment of time within anutterance. I-vectors can summarize a variety of characteristics of audiothat are independent of the phonetic units spoken, for example,information indicative of the age, gender, emotion, and/or dialect ofthe speaker.

The example of FIG. 3 illustrates processing to calculate an i-vector250 for a sample utterance 310. The server 120 accesses training data320 that includes a number of utterances 321. The training data 320 mayinclude utterances 321 including speech from different speakers,utterances 321 having different background noise conditions, andutterances 321 having other differences. Each of the utterances 321 isrepresented as a set of acoustic feature vectors. Each of the acousticfeature vectors can be, for example, a 39-dimensional vector determinedin the same manner that the acoustic feature vectors 240 are determinedin the example of FIG. 2.

The server 120 uses the utterances 321 to train a Gaussian mixture model(GMM) 330. For example, the GMM 330 may include 1000 39-dimensionalGaussians 331. The GMM 330 is trained using the acoustic feature vectorsof the utterances 321 regardless of the phones or acoustic states thatthe acoustic feature vectors represent. As a result, acoustic featurevectors corresponding to different phones and acoustic states are usedto train the GMM 330. For example, all of the acoustic feature vectorsfrom all of the utterances 321 in the training data 320 can be used totrain the GMM 330. In this respect, the GMM 330 is different from GMMsthat are trained with only the acoustic feature vectors for a singlephone or a single acoustic state.

When the sample utterance 310 is received, the server 120 determinesacoustic feature vectors that describe the utterance 310. The server 120classifies the acoustic feature vectors of the utterance 310 using theGMM 330. For example, the Gaussian 331 that corresponds to each acousticfeature vector of the sample utterance 310 may be identified. The server120 then re-estimates the Gaussians 331 that are observed in the sampleutterance 310, illustrated as re-estimated Gaussians 335 shown in dashedlines. As an example, a set of one or more acoustic feature vectors ofthe sample utterance 310 may be classified as matching a particularGaussian 331 a from the GMM 330. Based on this set of acoustic featurevectors, the server 120 calculates a re-estimated Gaussian 335 a havinga mean and/or variance different from the Gaussian 331 a. Typically,only some of the Gaussians 331 in the GMM 330 are observed in the sampleutterance 310 and re-estimated.

The server 120 then identifies differences between the Gaussians 331 andthe corresponding re-estimated Gaussians 335. For example, the server120 may generate difference vectors that each indicate changes inparameters between a Gaussian 331 and its corresponding re-estimatedGaussian 335. Since each of the Gaussians is 39-dimensional, eachdifference vector can have 39 values, where each value indicates achange in one of the 39 dimensions.

The server 120 concatenates or stacks the difference vectors to generatea supervector 340. Because only some of the Gaussians 331 were observedand re-estimated, a value of zero (e.g., indicating no change from theoriginal Gaussian 331) is included in the supervector 340 for each the39 dimensions of each Gaussian 331 that was not observed in the sampleutterance 310. For a GMM 330 having 1000 Gaussians that are each39-dimensional, the supervector 340 would include 39,000 elements. Inmany instances, Gaussians 331 and the corresponding re-estimatedGaussians 335 differ only in their mean values. The supervector 340 canrepresent the differences between the mean values of the Gaussians 331and the mean values of the corresponding re-estimated Gaussians 335.

In addition to generating the supervector 340, the server 120 alsogenerates a count vector 345 for the utterance 310. The values in thecount vector 345 can represent 0th order Baum-Welch statistics, referredto as counts or accumulated posteriors. The count vector 345 canindicate the relative importance of the Gaussians 331 in the GMM 330.The count vector 345 includes a value for each Gaussian 331 in the GMM330. As a result, for a GMM 330 having 1000 Gaussians, the count vector345 for the utterance 310 would include 1,000 elements. Each value inthe vector 345 can be the sum of the posterior probabilities of thefeature vectors of the utterance 310 with respect to a particularGaussian 331. For example, for a first Gaussian 331 a, the posteriorprobability of each feature vector in the utterance 310 is computed(e.g., the probability of occurrence of the feature vector as indicatedby the first Gaussian 331 a). The sum of the posterior probabilities forthe feature vectors in the utterance 310 is used as the value for thefirst Gaussian 331 a in the count vector 345. Posterior probabilitiesfor the each feature vector in the utterance 310 can be calculated andsummed for each of the other Gaussians 331 to complete the count vector345.

In the same manner that the supervector 340 and count vector 345 wasgenerated for the sample utterance 310, the server 120 generates asupervector 350 and a count vector 355 for each of the utterances 321 inthe training data 320. The GMM 330, the supervectors 350, and the countvectors 355 may be generated and stored before receiving the sampleutterance 310. Then, when the sample utterance 310 is received, thepreviously generated GMM 330, supervectors 350, and count vectors can beaccessed from storage, which limits the amount of computation necessaryto generate an i-vector for the sample utterance 310.

The server 120 uses the supervectors 350 to create a factor analysismodule 360. The factor analysis module 360, like the GMM 330 and thesupervectors 350, may be generated in advance of receiving the sampleutterance 310. The factor analysis module 360 can perform multivariatefactor analysis to project a supervector to a lower-dimensional vectorthat represents particular factors of interest. For example, the factoranalysis module may project a supervector of 39,000 elements to a vectorof only a few thousand elements or only a few hundred elements.

The factor analysis module 360, like the GMM 330, is trained using acollection of utterances, which may be the utterances in the sametraining data 320 used to generate the GMM 330. An adapted orre-estimated GMM may be determined for each of the i utterances [U₁, U₂,. . . , U_(i)] in the training data 320, in the same manner that there-estimated Gaussians 335 are determined for the utterance 310. Asupervector 350 [S₁, S₂, . . . , S_(i)] and count vector 355 [C₁, C₂, .. . , C_(i)] for each utterance [U₁, U₂, . . . , U_(i)] is alsodetermined. Using the vector pairs [S_(i), C_(i)] for each utterance,the factor analysis module 360 is trained to learn the common range ofmovement of the adapted or re-estimated GMMs for the utterances [U₁, U₂,. . . , U_(i)] relative to the general GMM 330. Difference parametersbetween re-estimated GMMs and the GMM 330 are then constrained to moveonly over the identified common directions of movement in the space ofthe supervectors. Movement is limited to a manifold, and the variablesthat describe the position of the difference parameters over themanifold are denoted as i-vectors. As a result, the factor analysismodule 360 learns a correspondence [S_(i), C_(i)]-->i-vector_(i), suchthat S_(i)/C_(i)=f(i-vectors), where f( ) is a linear function f(x)=T*xand T is a matrix.

The server 120 inputs the supervector 340 and count vector 345 for thesample utterance 310 to the trained factor analysis module 360. Theoutput of the factor analysis module 360 is the i-vector 250, whichincludes latent variables of multivariate factor analysis. The i-vector250 represents time-independent characteristics of the sample utterance310 rather than characteristics of a particular window or subset ofwindows within the sample utterance 310. In some implementations, thei-vector 250 may include, for example, approximately 300 elements.

FIG. 4 is a flow diagram that illustrates an example of a process forcustomizing a user interface based on characteristics of a speaker. Theprocess 400 may be performed by data processing apparatus, such as theclient device 100 described above or another data processing apparatus.

In step 402, the client device selects a user profile associated withthe user interface. For example, the client device may select a userprofile based on one or more of a password, voice recognition, speechrecognition, fingerprint recognition, or facial recognition. In someinstances, the client device may have a default user profile, in whichcase the client device typically selects and operates using the defaultuser profile.

In step 404, after selecting the user profile, the client device obtainsan audio signal encoding an utterance of the speaker. For example, theclient device may receive an utterance of the speaker at a microphone,and encode the utterance into an audio signal such as, for example, a 16kHz lossless audio signal.

The client device (optionally in combination with one or more servers),in step 406, processes the audio signal to identify one or morecharacteristics of the speaker. In some implementations, thecharacteristics may include one or more of an age, gender, emotion,and/or an dialect of the speaker. For example, the client device mayprovide the audio signal to a trained classifier (e.g., a neuralnetwork, SVM, or a Gaussian mixture model) that outputs likelihoodsassociated with one or more characteristics of the speaker. The clientdevice may then select characteristics having the highest likelihood,and/or apply a threshold to identify characteristics of the speaker.Alternatively or in addition, the client device may transmit the audiosignal to a server, which inputs the audio signal to a trainedclassifier, identifies characteristics of the speaker using theclassifier, and then transmits the identified characteristics back tothe client device.

Finally, in step 408, the client device customizes the user interfaceassociated with the user profile based on the identifiedcharacteristics. For example, the client device may change layout, fontsize, icon size, color scheme, wallpaper, icons and/or text to bedisplayed, animations, and any other items or settings for operation ofthe client device. In some cases, the client device may restrict accessto applications that were previously accessible, and/or provide accessto applications that were previously inaccessible. The client devicealso may, for example, restrict and/or modify the operation of one ormore applications executing on the client device. For example, theclient device may restrict a web browsing application to provide accessto only a limited set of websites.

In some implementations, the client device may also provide one or moreof the characteristics of the speaker to native and/or third-partyapplications executing on the client device. The client device mayprovide users with an option to decide whether to share this informationwith native and/or third-party applications.

FIG. 5 is a flow diagram that illustrates another example of a processfor customizing a user interface based on characteristics of a speaker.The process 500 may be performed by data processing apparatus, such asthe client device 100 described above or another data processingapparatus.

In step 502, the client device selects a user profile associated withthe user interface. The client device obtains an audio signal encodingan utterance of the speaker. For example, the client device may receivean utterance of the speaker at a microphone, and encode the utteranceinto an audio signal such as, for example, a 16 kHz lossless audiosignal.

In step 504, the client device (optionally in combination with one ormore servers) perform speech recognition, voice recognition, or both onthe audio signal to select and/or access the user profile associatedwith the user interface. In some instances, the client device may have adefault user profile, in which case the client device may provide accessto the default user profile when speech recognition and/or voicerecognition successfully authenticate the speaker.

The client device (optionally in combination with one or more servers),in step 506, also processes the audio signal to identify one or morecharacteristics of the speaker. In some implementations, thecharacteristics may include one or more of an age, gender, emotion,and/or dialect of the speaker. For example, the client device mayprovide the audio signal to a trained classifier (e.g., a neuralnetwork, SVM, or a Gaussian mixture model) that outputs likelihoodsassociated with one or more characteristics of the speaker. The clientdevice may then select characteristics having the highest likelihood,and/or apply a threshold to identify characteristics of the speaker.Alternatively or in addition, the client device may transmit the audiosignal to a server, which inputs the audio signal to a trainedclassifier, identifies characteristics of the speaker using theclassifier, and then transmits the identified characteristics back tothe client device.

Finally, in step 508, the client device customizes the user interfaceassociated with the user profile based on the identifiedcharacteristics. For example, the client device may change layout, fontsize, icon size, color scheme, wallpaper, icons and/or text to bedisplayed, animations, and any other items or settings for operation ofthe client device. In some cases, the client device may restrict accessto applications that were previously accessible, and/or provide accessto applications that were previously inaccessible. The client devicealso may, for example, restrict and/or modify the operation of one ormore applications executing on the client device. For example, theclient device may restrict a web browsing application to provide accessto only a limited set of websites.

In some implementations, the client device may also provide one or moreof the characteristics of the speaker to native and/or third-partyapplications executing on the client device. The client device mayprovide users with an option to decide whether to share this informationwith native and/or third-party applications.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, various formsof the flows shown above may be used, with steps re-ordered, added, orremoved.

Embodiments and all of the functional operations described in thisspecification may be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Embodiments may be implemented asone or more computer program products, i.e., one or more modules ofcomputer program instructions encoded on a computer-readable medium forexecution by, or to control the operation of, data processing apparatus.The computer readable-medium may be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter affecting a machine-readable propagated signal, or a combinationof one or more of them. The computer-readable medium may be anon-transitory computer-readable medium. The term “data processingapparatus” encompasses all apparatus, devices, and machines forprocessing data, including by way of example a programmable processor, acomputer, or multiple processors or computers. The apparatus mayinclude, in addition to hardware, code that creates an executionenvironment for the computer program in question, e.g., code thatconstitutes processor firmware, a protocol stack, a database managementsystem, an operating system, or a combination of one or more of them. Apropagated signal is an artificially generated signal, e.g., amachine-generated electrical, optical, or electromagnetic signal that isgenerated to encode information for transmission to suitable receiverapparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) may be written in any form of programminglanguage, including compiled or interpreted languages, and it may bedeployed in any form, including as a standalone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program may be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programmay be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification may beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows may also be performedby, and apparatus may also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Moreover, a computer may be embedded inanother device, e.g., a tablet computer, a mobile telephone, a personaldigital assistant (PDA), a mobile audio player, a Global PositioningSystem (GPS) receiver, to name just a few. Computer readable mediasuitable for storing computer program instructions and data include allforms of non-volatile memory, media and memory devices, including by wayof example semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory may be supplemented by, or incorporated in,special purpose logic circuitry.

To provide for interaction with a user, embodiments may be implementedon a computer having a display device, e.g., a CRT (cathode ray tube) orLCD (liquid crystal display) monitor, for displaying information to theuser and a keyboard and a pointing device, e.g., a mouse or a trackball,by which the user may provide input to the computer. Other kinds ofdevices may be used to provide for interaction with a user as well; forexample, feedback provided to the user may be any form of sensoryfeedback, e.g., visual feedback, auditory feedback, or tactile feedback;and input from the user may be received in any form, including acoustic,speech, or tactile input.

Embodiments may be implemented in a computing system that includes aback end component, e.g., as a data server, or that includes amiddleware component, e.g., an application server, or that includes afront end component, e.g., a client computer having a graphical userinterface or a Web browser through which a user may interact with animplementation of the techniques disclosed, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system may be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), e.g., the Internet.

The computing system may include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

While this specification contains many specifics, these should not beconstrued as limitations, but rather as descriptions of featuresspecific to particular embodiments. Certain features that are describedin this specification in the context of separate embodiments may also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment mayalso be implemented in multiple embodiments separately or in anysuitable subcombination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination may in some casesbe excised from the combination, and the claimed combination may bedirected to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems maygenerally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular embodiments have been described. Other embodiments arewithin the scope of the following claims. For example, the actionsrecited in the claims may be performed in a different order and stillachieve desirable results.

What is claimed is:
 1. A computer-implemented method comprising:receiving, by a digital assistant device that is shared by one or moreusers in a first class of users and one or more users in a second classof users, first data that encodes a user's utterance, and second datathat indicates, based on a feature vector representing time-independentcharacteristics of the entire user's utterance, that the user is amongthe one or more users in the first class of users that share the digitalassistant device, wherein: the feature vector representing thetime-independent characteristics of the entire user's utterance isobtained based on an analysis of one or more features derived from thefirst data that encodes the user's utterance; a neural network-basedclassifier is configured to: receive, as input, the feature vectorrepresenting time-independent characteristics of the entire user'sutterance; and generate, as output, an age classification probabilitydistribution that includes a first probability indicating that the useris among the one or more users in the first class of users and a secondprobability indicating that the user is among the one or more users inthe second class of users; the second data that indicates that the useris among the one or more users in the first class of users is not amanually-specified setting, and comprises an age classification for theuser determined based on the first probability being higher than thesecond probability in the age classification probability distributiongenerated as output from the neural-network based classifier; and thefirst class of users and the second class of users correspond todifferent age classifications; in response to receiving the second datathat indicates, based on the feature vector representing thetime-independent characteristics of the entire user's utterance, thatthe user is among the one or more users in the first class of users,generating, by the digital assistant device that is shared by the one ormore users in the first class of users and the one or more users in thesecond class of users, a user interface that (a) is customized, based onthe age classification for the user determined based on the featurevector representing the time-independent characteristics of the entireuser's utterance, to include characteristics targeted to one or more ofthe users of the first class of users that would not be present in aninterface that would be generated were the second data to indicate thatthe user is among the one or more users in the second class of usersthat is different from the first class of users and (b) does not permitaccess to one or more particular applications on the digital assistantdevice that the digital assistant device makes available throughinterfaced generated in response to second data that indicates that theuser is among the one or more users in the second class of users thatshare the digital assistant device; and providing, by the digitalassistant device that is shared by the one or more users in the firstclass of users and the one or more users in the second class of users,the generated user interface for output.
 2. The method of claim 1,wherein generating the user interface comprises generating the userinterface that includes icons that are larger than icons that would beincluded in an interface that would be generated were the second data toreflect that the user is among the one or more users in the second classof users that share the digital assistant device.
 3. The method of claim1, wherein generating the user interface comprises generating the userinterface that does not include text.
 4. The method of claim 1, whereingenerating the user interface comprises generating the user interfacethat includes less text than would be included in an interface thatwould be generated were the second data to reflect that the user isamong the one or more users in the second class of users that share thedigital assistant device.
 5. The method of claim 1, wherein generatingthe user interface comprises generating the user interface that onlyincludes controls that are limited to one or more controls for playinggames and a control for calling home.
 6. The method of claim 1, whereingenerating the user interface comprises generating the user interfacethat only includes controls that are limited to a control for callinghome and a control for accessing a camera application.
 7. The method ofclaim 1, wherein generating the user interface comprises generating theuser interface that includes an override option to cause generation ofthe interface that would be generated were the second data to reflectthat the user is among the one or more users in the second class ofusers that share the digital assistant device.
 8. The method of claim 1,further comprising limiting a number of pictures that can be taken witha camera application on the mobile device in response to receiving thesecond data.
 9. The method of claim 1, wherein the analysis is performedusing a neural network.
 10. The method of claim 1, wherein the seconddata indicates that the user is a minor.
 11. The method of claim 1,wherein generating the interface comprises: applying one or morecustomizations that are associated with one or more other speakers thathave a particular demographic characteristic that a neural networkidentifies as associated with the particular speaker; and changing, bythe mobile device, a mode of the digital assistant device from anunrestricted mode to another, different mode that prevents total,unrestricted access to the applications on the digital assistant device.12. The method of claim 1, further comprising, in response to receivingthe second data that (i) encodes the user's utterance, and (ii) reflectsthat the user is in the first class of users, operating the digitalassistant device to omit, from a search log, search queries receivedfrom the user.
 13. The method of claim 1, wherein: generating the userinterface comprises generating a safe mode user interface that isassociated with the first class of users that share the digitalassistant device; and providing the generated user interface for outputcomprises providing the generated safe mode user interface for output.14. The method of claim 13, wherein generating the safe mode userinterface comprises generating the safe mode user interface thatrestricts web pages accessible by a web browser on the mobile device andonly allows access to a previously selected set of applicationsdesignated for the first class of users that share the digital assistantdevice.
 15. A non-transitory computer-readable storage medium storinginstructions executable by a data processing apparatus and upon suchexecution cause the data processing apparatus to perform operationscomprising: receiving, by a digital assistant device that is shared byone or more users in a first class of users and one or more users in asecond class of users, first data that encodes a user's utterance, andsecond data that indicates, based on a feature vector representingtime-independent characteristics of the entire user's utterance, thatthe user is among the one or more users in the first class of users thatshare the digital assistant device, wherein: the feature vectorrepresenting the time-independent characteristics of the entire user'sutterance is obtained based on an analysis of one or more featuresderived from the first data that encodes the user's utterance; a neuralnetwork-based classifier is configured to: receive, as input, thefeature vector representing time-independent characteristics of theentire user's utterance; and generate, as output, an age classificationprobability distribution that includes a first probability indicatingthat the user is among the one or more users in the first class of usersand a second probability indicating that the user is among the one ormore users in the second class of users; the second data that indicatesthat the user is among the one or more users in the first class of usersis not a manually-specified setting, and comprises an age classificationfor the user determined based on the first probability being higher thanthe second probability in the age classification probabilitydistribution generated as output from the neural-network basedclassifier; and the first class of users and the second class of userscorrespond to different age classifications; in response to receivingthe second data that indicates, based on the feature vector representingthe time-independent characteristics of the entire user's utterance,that the user is among the one or more users in the first class ofusers, generating, by the digital assistant device that is shared by theone or more users in the first class of users and the one or more usersin the second class of users, a user interface that (a) is customized,based on the age classification for the user determined based on thefeature vector representing the time-independent characteristics of theentire user's utterance, to include characteristics targeted to one ormore of the users of the first class of users that would not be presentin an interface that would be generated were the second data to indicatethat the user is among the one or more users in the second class ofusers that is different from the first class of users and (b) does notpermit access to one or more particular applications on the digitalassistant device that the digital assistant device makes availablethrough interfaced generated in response to second data that indicatesthat the user is among the one or more users in the second class ofusers that share the digital assistant device; and providing, by thedigital assistant device that is shared by the one or more users in thefirst class of users and the one or more users in the second class ofusers, the generated user interface for output.
 16. Thecomputer-readable storage medium of claim 15, wherein generating theuser interface comprises generating the user interface that includesicons that are larger than icons that would be included in an interfacethat would be generated were the second data to reflect that the user isamong the one or more users in the second class of users that share thedigital assistant device.
 17. The computer-readable storage medium ofclaim 15, wherein the operations further comprise providing dataindicative of the classification results for multiple usercharacteristics to one or more applications executing on the digitalassistant device.
 18. The computer-readable storage medium of claim 15,wherein multiple user characteristics include an emotion of the user,and wherein the second data comprises a classification result indicativeof an emotion of the user determined based on the analysis of one ormore features derived from the first data that encodes the user'sutterance.